1. Field of the Invention
The present invention relates to a method of replacing a supporting bearing for a rolling roll, and more particularly, to the method of replacing the supporting bearing with a new supporting bearing having an increased rating load.
2. Related Art
In recent years, production facilities, particularly, operation rate of a rolling mill tends to be increased along with expansion of demands for steel products. Because of this increase of the operation rate, it has been conducted to increase rolling load and rolling speed.
However, there occurs a problem that life of a supporting bearing for supporting the rolling roll is decreased due to such increase of the rolling load and the rolling speed. For example, data show that in the supporting bearing for supporting backup rolls in a four step rolling mill, when the rolling load is increased by 10%, the life is decreased by 27%, when the rolling speed is increased by 10%, the life is decreased by 10%, and further, when the production is increased by 10%, the life is decreased by 10%. There are other data that when the rolling load, the rolling speed and the production are respectively increased by 10% at the same time, the life of the supporting bearing is decreased by 40%. In this case, serious influence is given to the rolling operation.
For the purpose of maintaining or prolonging the life of the supporting bearing, it has been considered to replace the supporting bearing which is in use at present for a new supporting bearing having an increased rating load. However, in order to replace the supporting bearings in the entire rolling mill at a time, new supporting bearings corresponding to the number of the rolling rolls must be prepared in advance, which requires an enormous replacing cost at a time. There is another problem that operation of the rolling mill must be stopped for a long time to conduct replacing works. Further, roll chocks and rolling rolls must be modified (worked) along with the replacement of the supporting bearings. In this case, it takes more time to conduct the replacing works, and the operation of the rolling mill must be stopped for a longer time.
There is a conventional art related to a structure for supporting the rolling roll which is disclosed in the following JP-A-2000-61512.